| Author | Weerayuth Sithsakonkul |
| Call Number | AIT RSPR no.TC-97-3 |
| Subject(s) | Optical fibers
|
| Note | A research study submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Advanced Technologies |
| Publisher | Asian Institute of Technology |
| Series Statement | Research studies project report ; no. TC-97-3 |
| Abstract | A system configuration is proposed in which the head-end transmits a discrete number of
optically modulated High-Definition TV (HDTV) signals together with a corresponding number
of local oscillator (LO) signals to facilitate heterodyne detection. This approach eliminates the
need for an expensive tunable laser at every subscriber terminal and allows sharing of head-end
costs among a large number of subscribers. Moreover, each optical HDTV signal is polarization
matched to its local-oscillator signal before transmission, and since they both undergo identical
changes in their states of polarization, expensive polarization control at the subscriber terminal
is also eliminated. The function of the optical detector thus is simply to down-convert the
optical signal to microwave frequencies for further multichannel heterodyne detection using a
tunable microwave local oscillator. Except for the final passive star coupler for local
distribution, the network is additionally rendered loss free through the use of compensating
Erbium-Doped Fiber Amplifiers (EDFA's).
Based on the use of Butterworth and Chebychev IF filters, we present channel allocation
criteria for specified crosstalk levels and highlight the trade-off between the number of channels
and the required tuning range of the microwave local oscillator. We assume that the selected
lasers have sufficiently narrow linewidths and we determine the dependence of bit-error rate
(BER) on the number of EDFA's, the average input power to each EDFA, the optical
bandwidth of EDF A's, the data rate, the splitting ratio of the final passive star coupler, and the
relative intensity noise from the signal and LO lasers.
Our results show that although the number of EDF A's only slightly degrades the system
performance, the maximum number of subscribers depends strongly on the number of EDF A's,
the gain of each EDF A, and the splitting ratio of the final passive star coupler. In addition, for
HDTV signals compressed to 100 Mbaud (Mb/s), careful design yields receiver sensitivities of
about -33 dBm (BER= 10-9
) allowing cost-effective delivery of about fifty HDTV channels to
about 100,000 subscribers. |
| Year | 1997 |
| Corresponding Series Added Entry | Asian Institute of Technology. Research studies project report ; no. TC-97-3 |
| Type | Research Study Project Report (RSPR) |
| School | School of Advanced Technologies (SAT) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Sharma, A. B. |
| Examination Committee(s) | Zhang, Jian-Guo;Rajatheva, Premanandana |
| Scholarship Donor(s) | His Majesty King Bhumibol Adulyadej, Thailand |
| Degree | Research Studies Project Report (M. Eng.) - Asian Institute of Technology, 1997 |